Semiconductor process

ABSTRACT

A semiconductor process of the present invention is described as follows. A substrate is provided, and a material layer is deposited on the substrate using an organic precursor as a reactant gas. A plasma treatment is conducted immediately after depositing the material layer, wherein plasma is continuously supplied during depositing the material layer and the plasma treatment. A pump-down step is conducted.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This divisional application claims the benefit of U.S. patentapplication Ser. No. 12/855,952, filed Aug. 13, 2010 currently pending,and is incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor process, and moreparticularly, to a method for reducing defects of a deposited film.

2. Description of Related Art

Along with rapid progress of semiconductor technology, the dimensions ofsemiconductor devices are reduced and the integrity thereof promotedcontinuously to further advance the operating speed and performance ofintegrated circuits (ICs). As the demand for device integrity is raised,any tiny defects formed on a deposited film have to be considered toavoid a great impact on the operating speed and performance of thecircuit.

Nowadays, many material layers are formed through chemical vapordisposition (CVD) in the presence of plasma, which uses a precursorcontaining organic molecules as a reactant gas. After a demandedmaterial layer is formed on a substrate and reaches the pre-determinedthickness, the source for the reactant gas is turned off to stop thedeposition. The remaining reactant gas, however, would continue todissociate and react on the surface of the material layer, therebyforming tiny defects thereon. To describe more in detail, after thedisposition process using plasma, dangling bonds formed on the filmsurface may capture the residual radicals or ionic groups dissociatedfrom the precursor, such that the radicals or ionic groups are prone tocongregate and adhere in clusters on the surface of the material layerto form the particles with the size less than 0.05 μm, that is, the tinydefects. These tiny defects may be further exaggerated after forming asubsequent layer on the material layer in the follow-up step. Theresultant defects with the size greater than 0.05 μm are formed on thesurface of the subsequent layer, and thereby can be detected. As aresult, such defects may seriously impact the subsequent process andproduct reliability.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a semiconductorprocess which can reduce the number of particles on a deposited materiallayer, thereby improving film qualities and overall reliability.

A semiconductor process of the present invention is described asfollows. A substrate is provided, and a material layer is deposited onthe substrate using an organic precursor as a reactant gas. A plasmatreatment is conducted immediately after depositing the material layer,wherein plasma is continuously supplied during depositing the materiallayer and the plasma treatment. A pump-down step is conducted.

According to an embodiment of the present invention, the semiconductorprocess further includes conducting a purge step between the plasmatreatment and the pump-down step.

According to an embodiment of the present invention, the organicprecursor includes an organosiloxane-based precursor. Theorganosiloxane-based precursor is selected from the group consisting oftetraethyl orthosilicate (TEOS; Si(OC₂H₅)₄),1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS; C₄H₁₆O₄Si₄),dimethyldimethoxysilane (DMDMOS; C₄H₁₂O₂Si) andoctamethylcyclotetrasiloxane (OMCTS; C₈H₂₄O₄Si₄).

According to an embodiment of the present invention, the organicprecursor is supplied from a liquid system through gasification.

According to an embodiment of the present invention, a gas source usedfor the plasma treatment includes inert gas or oxygen or hydrogen.

According to an embodiment of the present invention, a flow rate of agas source used for the plasma treatment is within a range of 1000 sccmto 40000 sccm.

According to an embodiment of the present invention, a power used forthe plasma treatment is within a range of 100 W to 4000 W.

According to an embodiment of the present invention, a temperature usedfor the plasma treatment is within a range of 300° C. to 500° C.

According to an embodiment of the present invention, a pressure used forthe plasma treatment is within a range of 0.5 Torr to 20 Torr.

A semiconductor process of the present invention is described asfollows. A substrate is provided in a chamber. A reactant gas containingan organic precursor is introduced into the chamber. A material layer isdeposited on the substrate in a presence of plasma. The reactant gas isturned off and the plasma is supplied continuously during a plasmatreatment after the material layer is formed. A pump-down step isconducted.

According to an embodiment of the present invention, the semiconductorprocess further includes conducting a purge step between the plasmatreatment and the pump-down step.

According to an embodiment of the present invention, the organicprecursor includes an organosiloxane-based precursor. Theorganosiloxane-based precursor is selected from the group consisting oftetraethyl orthosilicate (TEOS; Si(OC₂H₅)₄),1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS; C₄H₁₆O₄Si₄),dimethyldimethoxysilane (DMDMOS; C₄H₁₂O₂Si) andoctamethylcyclotetrasiloxane (OMCTS; C₈H₂₄O₄Si₄).

According to an embodiment of the present invention, the organicprecursor is supplied from a liquid system through gasification.

According to an embodiment of the present invention, a process conditionfor the plasma treatment is substantially the same as a processcondition for depositing the material layer, except the reactant gas.

According to an embodiment of the present invention, the plasma suppliedduring the plasma treatment is generated by a high-frequency power.

As mentioned above, the semiconductor process according to the presentinvention includes conducting a plasma treatment immediately after thedeposition of the material layer using the organic precursor. Since theplasma is continuously supplied during depositing the material layer andthe plasma treatment, the residual radicals or ionic groups dissociatedfrom the organic precursor cannot react with the surface of the materiallayer. As a result, the formation of tiny defects or clustered particlescan be minimized in number. Moreover, the semiconductor process which iscarried out by a simple plasma treatment can be easily incorporated intothe current fabrication process.

In order to make the aforementioned and other features and advantages ofthe present invention more comprehensible, preferred embodimentsaccompanied with figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a flow chart illustrating a semiconductor process according toan embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

The semiconductor process of the present invention is applicable to afilm deposition process involving a precursor with relatively lowactivation energy, e.g. an organic precursor. After a material layer isformed using the organic precursor as a reactant gas, a plasma treatmentis conducted immediately after the film deposition, so as toefficaciously eliminate the dangling bonds on the surface of thematerial layer and thus prevent the residual radicals or ionic groups ofthe organic precursor from clustering and adhering thereon. It should benoticed that the plasma is continuously supplied during the filmdeposition and the plasma treatment without interruption.

In details, a gas source used for the plasma treatment at least includesan inert gas or oxygen (O₂) or hydrogen (H₂), and a flow rate thereofcan be within a range of 1000 sccm to 40000 sccm. A power used for theplasma treatment may be within a range of 100 W to 4000 W. A temperatureused for the plasma treatment may be within a range of 300° C. to 500°C. A pressure used for the plasma treatment may be within a range of 0.5Torr to 20 Torr.

The implementation of the present invention is further described in amanner of a flow chart hereinafter. For illustration purposes, thefollowing disclosure is described in terms of fabricating a dielectricfilm, which is illustrated only as an exemplary example in practice andthereby enables those of ordinary skill in the art to practice thisinvention, and should not be adopted for limiting the scope of thepresent invention. FIG. 1 is a flow chart illustrating a semiconductorprocess according to an embodiment of the present invention.

Referring to FIG. 1, in step S100, a substrate is provided. Thesubstrate is placed in a deposition chamber, such as a chemical vapordeposition (CVD) chamber with plasma assistance. The substrate can be asemiconductor wafer, e.g. an N- or P-type silicon wafer, whereon thinfilms, conductive parts, or even semiconductor devices may be formed. Inan embodiment, a process pressure and a process temperature are furtherset in the deposition chamber, so as to obtain an appropriate depositioncondition for subsequent procedures. The process pressure for filmdeposition may be within a range of 0.5 Torr to 20 Torr, possibly 5Torr. The process temperature for film deposition may be within a rangeof 300° C. to 500° C., possibly 400° C.

In step S102, a reactant gas is introduced into the chamber, wherein thereactant gas contains an organic precursor, which may be supplied from aliquid system through gasification. The organic precursor havingrelatively low activation energy is, for example, anorganosiloxane-based precursor which can be selected from the groupconsisting of tetraethyl orthosilicate (TEOS; Si(OC₂H₅)₄),1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS; C₄H₁₆O₄Si₄),dimethyldimethoxysilane (DMDMOS; C₄H₁₂O₂Si) andoctamethylcyclotetrasiloxane (OMCTS; C₈H₂₄O₄Si₄). In an embodiment, whenTEOS is selected as the organic precursor, the reactant gas may furthercontain oxygen (O₂). An inert gas, such as helium (He), argon (Ar) ornitrogen (N₂), may also be introduced into the chamber as a carrier gasor a diluting gas during the step S102.

Afterwards, plasma is generated in the chamber, and the decomposedreactant gas reacts on the substrate to deposit a material layer in thepresence of the plasma (step S104). The material layer can be made ofsilicon oxide or a low-k material with a dielectric constant less than4, depending on the chosen organic precursor. In an embodiment, radiofrequency (RF) power is applied to the chamber for generating theplasma, wherein a high-frequency power and a low-frequency power may beutilized simultaneously during the deposition process. The appliedhigh-frequency power is, for instance, within a range of 100 W to 4000W, possibly about 280 W of the high-frequency power and 60 W of thelow-frequency power.

In step S106, after the material layer is formed on the substrate andreaches the pre-determined thickness, the organic precursor source forthe reactant gas is turned off, while the plasma is continuouslysupplied to the deposition chamber, so as to conduct a plasma treatmentin situ. As the organic precursor source is turned off, the depositionof the material layer is stopped, such that the plasma treatment isconducted directly after the deposition of the material layer to avoidthe formation of the defects. In practice, during the plasma treatment,the low-frequency power can be turned off, but the high-frequency poweris still provided. The high-frequency power during the plasma treatmentcan be the same as that during the deposition of the material layer,i.e. within the range of 100 W to 4000 W, preferably about 280 W.Accordingly, the plasma is continuously supplied during the materiallayer deposition and the subsequent plasma treatment withoutinterruption therebetween.

The time period or duration of conducting the plasma treatment is, forexample, greater than 0 second, preferably about 3 seconds. The flowrate of the gas provided in the plasma treatment can be within a rangeof 1000 sccm to 40000 sccm, preferably about 9000 sccm. The temperatureused for the plasma treatment may be within a range of 300° C. to 500°C., preferably about 400° C. The pressure used for the plasma treatmentmay be within a range of 0.5 Torr to 20 Torr, preferably about 5 Torr.Alternatively, in an embodiment, the organic precursor source and theoxygen (O₂) source for the reactant gas can both be turned off, whilethe carrier gas source is supplied continuously during the plasmatreatment. That is to say, the process condition for the plasmatreatment can be substantially the same as the process condition fordepositing the material layer, except for the reactant gas source.

After the step S106, a purge step can be optionally conducted (stepS108). During the purge step, the plasma is not provided anymore. In anembodiment, the high-frequency power supply is turned off, while thecarrier gas source is still provided. The carrier gas source canfunction as the purge gas injected into the deposition chamber forpurging the chamber from the remaining reactant gas or impurities. Theduration of conducting the purge step is, for example, within a range of0 seconds to 10 seconds, preferably about 3 seconds. In addition, theflow rate of the purge gas during the purge step is usually about 1000sccm to 40000 sccm, preferably about 9000 sccm. At this moment in theprocess, the pressure and the temperature in the chamber may be bothidentical with the process pressure and the process temperature that areset previously.

In step S110, a pump-down step is conducted, so as to pump down thepressure in the chamber to a base pressure less than about 0.2 Torr.After the pump-down step is finished, the substrate may wait to betransferred out from the deposition chamber for further processes tocomplete fabrication of demanded semiconductor devices, which are wellappreciated by persons skilled in the art, and thus, the detaileddescriptions thereof are not described herein.

It should be noted that once the material layer is deposited as desired,the plasma treatment is performed with the uninterrupted plasma. Sincethe material layer is exposed to the continuously-supplied plasmatreatment, the dangling bonds on the surface of the material layer canbe bombarded and thus eliminated. Accordingly, the residual radicals orionic groups dissociated from the organic precursor would not react withor adhere to the surface of the material layer, such that the formationof tiny defects, e.g. clustered particles, can be effectively minimizedin number. In other words, after the advantageous semiconductor processillustrated above, the resultant material layer with minimized number ofdefects or particles formed thereon can be obtained owing to theuninterrupted plasma provision (i.e. plasma treatment) immediately afterthe deposition of the material layer. It is also emphasized that ifthere is an idle of plasma provision between the plasma treatment andthe deposition of the material layer, the interrupted plasma treatmentwould scarcely exhibit the foregoing efficacy of reducing the defects.

Moreover, the above embodiment in which the material layer is exposed tothe plasma of the carrier gas is provided for illustration purposes, andshould not be construed as limiting the scope of the disclosure.Certainly, in other embodiments, plasma of other gases can also beutilized in the plasma treatment as long as the provision of plasma iscontinuous during deposition of the material layer and the plasmatreatment. Other applications and modifications should be apparent tothose of ordinary skill in the art according to the above-mentionedembodiment, and are not specifically restricted in the presentinvention.

To substantiate the outstanding efficacy of the plasma treatment in thesemiconductor process, actual measurement of the defects formed on thesurface of the material layer according to several examples will bedescribed hereinafter. It should be appreciated that the followingexamples are provided merely to illustrate the effects upon thereduction of the defects in the present invention, but are not intendedto limit the scope of the present invention.

Table 1 depicts testing results that are represented by count number ofthe particles with the size greater than 0.05 μm formed on the materiallayers implemented by the abovementioned method respectively accordingto Examples 1-3 and

Comparative Examples 1-2.

TABLE 1 Organic He plasma Particles precur- Idle treatment He purge(size >0.05 sor (second) (second) (second) μm) (EA) Example 1 TEOS 0 3 040 Example 2 TEOS 0 3 3 15 Example 3 TEOS 0 3 10 23 Comparative TEOS 0 03 ~10000 Example 1 Comparative TEOS 1 3 3 ~10000 Example 2

In Table 1, Example 1 stands for the condition that a plasma treatmentis conducted immediately after a film deposition without an idle ofplasma provision therebetween, but a subsequent purge step is absentbefore a pump-down step. Likewise, Examples 2 and 3 stand for theconditions that the plasma treatment is conducted immediately after thefilm deposition without an idle of plasma provision therebetween, andthe subsequent purge step is then conducted before a pump-down step.Comparative Example 1 stands for the condition that only the purge stepis conducted between the film deposition and the pump-down step withoutany plasma treatment. Comparative Example 2 stands for the conditionthat the plasma treatment and the purge step are conducted in sequencebetween the film deposition and the pump-down step, but there is an idleof plasma provision between the plasma treatment and the filmdeposition.

As shown in Table 1, it is obvious in Examples 1-3 that the continuousplasma treatment can effectively reduce the number of particles ascompared with Comparative Example 1, while the absence of the purge stepmerely makes a minor impact on particles reduction. According to thecomparison between Example 2 and Comparative Example 2, the idle ofplasma provision between the plasma treatment and the film depositionwould ruin the outstanding effect of plasma treatment upon particlesreduction. Based on the above results, the plasma treatment has to beconducted directly after the film deposition with continuously-providedplasma, and the purge step after the plasma treatment can be optionallyselected as a procedure to further minimize the particle formation.

In view of the above, the semiconductor process according to anembodiment of the present invention includes conducting a plasmatreatment immediately after the deposition of the material layer usingthe organic precursor. Once the material layer is exposed to thecontinuously-supplied plasma treatment, the dangling bonds on thesurface of the material layer can be eliminated, and it is thusdifficult for the residual radicals or ionic groups dissociated from theorganic precursor to adhere thereon. Hence, the number of tiny defectsor clustered particles can be effectively reduced, and the resultantmaterial layer can possess improved film qualities which benefitsgreatly by the plasma treatment.

In addition, the semiconductor process of the present invention relieson the plasma treatment through the continuous provision of plasmabetween the film deposition and the pump-down step, so as to easily beincorporated into the current process. Thus, not only the process issimple, the product reliability can be more effectively enhanced.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A semiconductor process, comprising the followingsteps in the sequence set forth: providing a substrate in a chamber;introducing an organic precursor and a reactant gas into the chamber;depositing a material layer on the substrate in a presence of plasma;turning off the organic precursor and continuing to supply the plasmaduring a plasma treatment after the material layer is formed; andconducting a pump-down step.
 2. The semiconductor process according toclaim 1, further comprising conducting a purge step between the plasmatreatment and the pump-down step.
 3. The semiconductor process accordingto claim 1, wherein the organic precursor comprises anorganosiloxane-based precursor.
 4. The semiconductor process accordingto claim 3, wherein the organosiloxane-based precursor is selected fromthe group consisting of tetraethyl orthosilicate (TEOS; Si(OC2H5)4),1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS; C4H16O4Si4),dimethyldimethoxysilane (DMDMOS; C4H12O2Si) andoctamethylcyclotetrasiloxane (OMCTS; C8H24O4Si4).
 5. The semiconductorprocess according to claim 1, wherein the organic precursor is suppliedfrom a liquid system through gasification.
 6. The semiconductor processaccording to claim 1, wherein the reactant gas comprises oxygen.
 7. Thesemiconductor process according to claim 1, wherein the plasma suppliedduring the plasma treatment is generated by a high-frequency power. 8.The semiconductor process according to claim 1, wherein the plasma isgenerated with a first radio frequency power and a second radiofrequency power having a lower frequency than that of the first radiofrequency, and the second radio frequency power is turned offimmediately after depositing the material layer.
 9. The semiconductorprocess according to claim 1, further comprising providing a carrier gaswhich comprises helium (He), argon (Ar) or nitrogen (N₂).
 10. Thesemiconductor process according to claim 9, wherein the pump-down stepis performed after terminating providing the reactant gas while keepingproviding the carrier gas with the plasma treatment.